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Do I Need An Air Exchanger?

Here's a startling fact.
70,000 Americans die each year from Dirty Air... Millions more are hospitalized or sickened...

Indoor Air Quality is often worse than polluted outside air...

According to the EPA; concentrations of toxic pollutants can be up to ten times greater inside a home than outside, even in our smoggiest cities. And today's homes, while more energy efficient, can trap contaminants like formaldehyde, radon, and household chemicals inside.

Invisible pollutants produced by common household substances, plus dust and excess humidity that get trapped in today's houses, can increase your risk of chronic respiratory illness and your home's risk of serious structural damage.

Excess Humidity
Today's well-insulated homes often lack the ability to "breathe" freely. Trapped, stale air and excess humidity can lead to mould build-up, unpleasant odours, condensation on windows, and even structural damage to your home.

More than 50% of all homes show signs of high basement humidity.*

*Source: Canada Mortgage and Housing Corporation (CMHC)

Dust, Chemicals, Aerosols and Other Common Pollutants
Pervasive irritants such as dust, dust mites, cigarette smoke and other pollutants commonly found in household air may increase the risk of chronic respiratory illness, allergies, sinusitis, frequent headaches, coughing and asthma.

The rate of asthma has increased by 160% over the last 15 years.*


Primary Sources of Indoor Air Pollution
The word pollution is often associated with large clouds of smoke emerging from factory smoke stacks, automobiles, etc. In fact, the majority of people blame poor indoor air quality on outdoor air pollution. But this is not true! Outdoor air pollution only counts for a fraction of indoor air pollution.

These Are The Main Sources Of Indoor Air Pollution:

Asbestos, Insulation, Fiberglas, Dust & Dust Mites
High Humidity Levels, Unpleasant Odours, Mould, Carbon Monoxide (CO), Fireplace/Smoke, Firewood, Radon, Solvents, Woodstove, Dust & Dust, Mites, Combustion System, Paints & Chemicals, Household Cleaners
Excess Humidity, Personal Hygiene, Products (Aerosols, Sprays, Etc.), Mould Spores
Allergens, Carpet, Dust & Dust Mites, Pet Hair and Dander, Carbon Dioxide (CO2)
Printers, Photocopiers: Ozone, Volatile Organic Compounds (VOC), Melamine Furniture (Harmful Vapours, VOC, And Formaldehyde)
Carbon Monoxide (CO), Gas, Pesticides/Herbicides, Solvents, Dust, Paints & Chemicals, Cleaning Agents
Carpet, Fireplace, Dust & Dust Mites, Allergens, Second-Hand Smoke, Humidifiers, Pet Hair and Dander
Lingering Odours, Bacteria, Cooking Pollutants

Six Essential Steps To Healthy Indoor Air

The Soup Concept
Indoor air is like a soup with a variety of pollutants in it. Most of these indoor air contaminants are known to cause or contribute to a long list of health and each of these pollutants requires its own strategic solution in order to eliminate them from the air you inhale.

It is difficult to write this article knowing that so many of the points mentioned below could be elaborated on in much greater detail, nonetheless this short article should serve as a general guide for understanding the basic steps to cleaner indoor air.

There are six steps in total that must be followed; miss one and you compromise your indoor air quality and your health. Use the acronym "EFVOID", to outline these strategic steps:

E = Elimination
Eliminate or reduce as many obvious indoor air pollutant sources as is reasonably possible. These would include but are not limited to the following: Un-maintained or very old carpet, especially if laid over concrete, dust accumulation in air ducts, all visible mould growth no matter the amount, indoor pesticides, perfumes, hair sprays, animal dander, cat boxes, unsealed paint cans, indoor smoking of tobacco products, metabolic sewer gasses from unused plumbing fixtures, candle burning, unencapsulated man-made building materials, and plug-in, spray, or standing deodorizers that emit man-made chemicals. Laundry and cleaning products, personal care products, etc. that you can purchase without chemical fragrances will be most advantageous to reduce exposure and indoor related health problems.

Many of the indoor air pollutant sources mentioned above are common sense when given a thought, yet the cumulative affect is often overlooked. Eliminate as many as you reasonably can. In some cases a professional air quality inspection may be in your best interest to assure you are not missing indoor air pollutant sources such as sewer gas entry, small combustible gas leaks, areas of hidden mould, negative air pressure problems, or ventilation/heating/cooling failures or inadequacies. This is especially important for those homes where occupants have already begun experiencing any of the indoor air quality symptoms listed at

F = Filtration
Use good air filtration. This entails the use and maintenance of quality furnace, the possible use of high efficiency particulate air filters (HEPA) in rooms, particularly if you do not have a ducted air handling system, and lastly, a high quality vacuum cleaner which does not allow ultra-fine particles to re-circulate back into the air. Reducing airborne particles with the use of good filtration techniques will improve indoor air quality by making indoor air less dense of particle pollutants and consequently easier to inhale. This will also reduce physical irritation that causes allergy and asthma symptoms. It is additionally important to never feather dust your home or sweep hardwood flooring. Sweeping and feather dusting launch massive amounts of particles back into the air. Dust these areas with damp cloths or mops, or vacuum with a quality vacuum cleaner to prevent acute exposure.>/p>

V = Ventilation
The first thing ventilation entails is circulating your indoor air by using your ducted air handling system (if you have one), even if you are not air conditioning or heating. Air should be circulated continuously, or at minimum, at critical times of each day during high activity when significant amounts of airborne particles are being created (when people are changing clothes or during high activity periods indoors). Circulating indoor air helps to scrub airborne particles from your air (provided you are using quality air filters in your air handling system) and helps to prevent dead air space and micro climates were mould can take hold. Circulating your indoor air also helps true air purification systems to work more efficiently by mixing the air in your indoor environment.

Secondly, ventilation includes opening windows frequently to allow replenishing of indoor oxygen levels. This is essential because there is nothing in indoor environments that "makes" oxygen for you. Maintaining good oxygen levels will help reduce headaches, tiredness and fatigue while increasing mental alertness and improving overall health. Opening windows should be done whenever needed, all year long. If the weather is extremely hot or cold, the indoor air exchange process will be expedited by default. This is due to the differences in outdoor and indoor air temperatures. During extreme temperature differences windows can be closed again very soon after opening them.

Third, ventilation includes the use of exhaust fans to remove bathroom odours, moisture from showering and cooking, and to reduce exposure to chemicals in hair spray or other aerosol products.

O = Ozonation
Ozone, also known as "activated oxygen", is one of natures ingredients for purifying outdoor air and is absolutely essential in the elimination of indoor pollutants. Indoor ozone levels should be constantly maintained to the same levels as those found naturally over the entire planet. Ozone oxidizes chemical gasses and eliminates virtually all odours. Ozone also helps control viruses, bacteria and mould growth. Ozone is the primary reason we always go OUT for fresh air and is the sole reason for the fresh air smell outdoors. Proper indoor ozone replacement can only be accomplished by using a true air purifier with adjustable ozone output.

I = Ionization
Ions are the second ingredient that nature uses for cleaning the outdoor air of particulate (physical matter floating in air) and are another essential for indoor air quality. Indoor ions must be maintained in the right amount, and in the right ratio of positive ions to negative ions, just like nature produces outdoors. Ions are effective for indoor particle reduction even if no filtration is used, albeit you should still use filters if you can. Ions also work on particles that are so small they would pass through virtually any man-made filter media and vacuum bags. Furthermore, ions inadvertently help eliminate odours by reducing odor carrying particles from sources such as mould spores and airborne fecal and urine matter. Ion replacement is accomplished by using a true air purifier with constant ion output.

D = Dehumidification
Maintaining indoor humidity levels at or below 50% is absolutely essential to help protect your indoor air from bio-contaminants such as mould, bacteria, insects, mites and their related metabolic gasses and excrement. Most indoor environments today require dehumidification. A humidity gauge is the only way to know if your humidity is within safe parameters year round.

Follow the six steps above and your indoor air quality will be as good as it can be. Miss just one of these steps and your air quality will certainly be degraded or compromised.

Air Exchangers

Air Exchanger Basics
With the emphasis on energy conservation and efficiency, new home construction can create a problem of indoor air pollution. Vapour barriers, thermal windows, weather-stripping and caulk have reduced or stopped fresh air from infiltrating and replacing stale air. Entering and exiting the house through doors isn't always enough air changes. Cooking, aerosol sprays, cleaning agents, paints, and in some cases excess humidity if the house is sealed too tightly can create an undesirable environment. Keeping windows or doors open does not conserve energy. A device known as an air-to-air exchanger is used to recover heating or cooling and improve air quality.

Air Exchanger Functions- Air Detectives

Heat-recovery air exchangers capture heat from stale moist air and transfer that heat to the fresh air intake so that your heating system will not have to work so hard to condition that air.

Air-to Air Exchangers

By Building Inspector and Indoor Air Specialist, Dan Schilling
© Copyright 2002 Residential Inspections LLC, All Rights Reserved

Air-to-air exchangers (top left), sometimes called heat recovery ventilators, may go by different brand names, but they all have the same primary function of introducing fresh air from the outdoors into the interiors of homes. The reason they are sometimes called heat recovery ventilators is because they temper the cold incoming air by extracting heat from the stale air being simultaneously exhausted. These devices are being heavily promoted and sold by some HVAC contractors and, in some states, they are an option to fulfill new construction code requirements designed to improve indoor air quality.

Provided that these devices are diligently maintained, and I repeat "diligently" maintained, they can be an advantageous appliance to have installed in a home or office building. On the other hand, air-to-air exchangers should never be considered a viable solution to the indoor air contamination problems causing such a wide array of health concerns. Furthermore, if not consistently maintained, these devices can become seriously detrimental, increasing the contamination of indoor air.

Allow me to share a list of what I regard as the advantages and disadvantages of these air-to-air exchangers/heat recovery ventilators.

Air-to-air exchangers bring in small amounts of oxygenated air into a home on a varying basis, depending on how the system is installed. This influx of oxygenated air is typically introduced directly into the interior of the air duct system and then distributed through the ducts. When considering that each human in a home breathes about 2,500 gallons of air every day, one begins to understand the benefit of replacing oxygenated air indoors. Replacing oxygenated air to the indoor environment can help us feel more energetic, mentally alert, and reduce symptoms associated with high levels of carbon dioxide (CO2). While carbon dioxide should not be confused with highly poisonous carbon monoxide (CO), high levels of carbon dioxide can also cause poor health affects, such as headaches, dizziness, drowsiness, shortness of breath and eye irritation.

Air-to-air exchangers assist in the removal of indoor moisture which could lead to mould and bacterial contamination of indoor air. The amount of moisture actually being eliminated from the indoor environment may be nominal in comparison to the amount of moisture created within a home, however, even small amounts of moisture removal are a step in the right direction. This is particularly true for newly constructed homes and homes that have otherwise been made more energy efficient.

Rancid indoor air is a serious problem in virtually all indoor environments. Adding a small percentage of oxygenated air to an indoor environment does not solve the indoor pollution problems we have today. It is very misleading to presume that these devices are an answer to indoor air quality. Contamination sources and elimination methods are very complex and often require a variety of measures to correct and improve indoor air quality. As I have said many times before, there is no silver bullet.

Air-to-air exchangers typically will not remove enough moisture from the indoor air to eliminate moisture related problems, hence, all other methods of indoor moisture control must still be considered. High levels of moisture are known to be the leading cause of biological contamination found in indoor air.,/p>

Similar to the evaporator media used in built-in humidifiers and the fins of the air conditioner evaporator coil (both hidden from view inside duct work), the media inside of a typical air-to-air exchanger also secretly collects dust particles. These particles can promote hidden mould growth and can potentially circulate the mould spores into the breathable air. As an air quality inspector, I never recommend any unnecessary media that can promote hidden bio-growth within the air circulation system.

Electrical ions, richly present in the air outdoors and vital to cleaning ultra-fine particles from the air, are not brought in through air-to-air exchangers. It is unlikely that the beneficial ions would make it past the outdoor intake vent, much less through the ducts of the system. Ions lose their electrical charge the moment they touch something, such as the interior of ducts or filter media. Therefore, air-to-air exchangers are an inadequate solution for the removal of particulate pollutants that cause many ill health affects.

Naturally "activated" oxygen, also called "ozone" (not to be confused with manmade pollution levels), is also present in the air outdoors and is necessary for eliminating foul odours and chemical gasses through a process called oxidation. Ozone is what leaves that fresh, clean smell in the air outdoors. Air-to-air exchangers may bring in small amounts of activated oxygen, but not nearly enough to maintain natural outdoor levels for proper indoor air purification. This is particularly true in new or remodeled homes where the rate of off-gassing chemicals from building materials is excessive. Due to the half-life of ozone, one would have to leave all house windows wide open 24 hours a day in order to maintain the outdoor purification levels of ozone. This is highly impractical for most of us. Many are now turning to residential air purifiers as a practical way to replace the missing ozone. (Note: Air purifiers that produce ozone indoors should have complete adjustability of ozone output.)

Air-to-air exchangers require regular maintenance, which is almost never performed by homeowners, and likely to be overlooked by contractors during service calls. In fact, at the time of this article, I have yet to see one of these air-to-air exchangers properly maintained while conducting building inspections. Internal motors do not get oiled, allowing them to dry up, heat up and seize. The interior filters are not cleaned and, perhaps worst of all, the air intakes from the exterior are quite frequently clogged with dirt. Often they are so clogged that an ant couldn't get through, much less a supply of fresh air. If outdoor air cannot enter, there is no benefit whatsoever.

When the air intake vents (middle left) get clogged (bottom left), these systems which were intended to improve indoor air quality can become a detrimental health hazard. When clogged, air-to-air exchangers can make the indoor air significantly worse than it would be without the system installed at all. This point should be further emphasized by saying that clogging is a matter of when, not if. The reason for this has to do with indoor air pressures: When the intake vent gets clogged and the system can no longer bring in air from outdoors, it will still continue to exhaust air from the indoors. This creates "negative air pressure" within the home, which in turn can cause serious air quality issues due to a process called "back-drafting". In essence, back-drafting causes critically important exhaust vents in the home to function poorly, or operate in reverse. Consequences of negative indoor air pressure and back-drafting are: A) prevents kitchen and bathroom exhaust fans from operating properly, which can over tax and burn out their motors faster, B) causes excessive indoor moisture levels which in turn causes health problems related to moulds and dust mite populations, C) causes exhaust vents from furnaces, water heaters, gas ranges and fireplaces to function poorly, or in reverse, thus spilling poisonous carbon monoxide gasses and other combustion pollutants into breathable air, D) increases the infiltration rate of radioactive radon gas through the basement area of a home which increases the risk of lung cancer for the occupants of the home.

If the interior filter, designed to protect the heat transfer portion of the system, becomes clogged with house dust, the system can no longer exhaust the stale indoor air properly. If the system still has the ability to pull outdoor air into the home without the ability to exhaust an equal amount of air, the indoor air pressure can become "positive". This positive indoor air pressure can cause "exfiltration" which pushes moisture-laden indoor air into the walls of the house, through electrical outlets, switches, light fixtures, box sills, and floor boards. Consequences of moisture exfiltration are: A) moisture can accumulate in wall cavities where it can begin rotting the structural frame of a home, B) the moisture rusts metal plate fasteners of floor and truss members which can lead to collapse, C) the moisture can cause the walls and floors to change shape, D) moisture attracts wood-destroying insects into wall cavities, E) cause paint to peel on exterior walls, F) moisture can wet and damage insulation causing energy loss.

Note: As you can see, positive indoor air pressure can adversely affect the structure of your home while negative air pressure adversely affects the health and safety of the occupants. Ideally, indoor air pressure should be as close to neutral as possible.

The installed price of an air-to-air exchanger can be $1,500.00 to $3,000.00 each.

In summary, if you bought a home that did not have an air-to-air exchanger, I would recommend you do not purchase one. For the benefit of a little oxygen, you could open your windows on occasion, save the maintenance hassles and use the money for more important air quality improvements. If you bought a home that already had an air-to-air exchanger, keep it scrupulously maintained or disconnect it.

Three Better Solutions

In addition to proper cleaning and elimination of obvious sources of indoor air contaminants, I recommend that homeowners use a combination of the three proven methods of air quality control listed below. These methods will significantly improve indoor air quality at a fraction of the cost of an air-to-air exchanger:

Efficient Furnace Filters
Good furnace filtration, such as the high-efficiency pleated type or good quality electrostatic filters will provide:

  • A significant reduction of particles in the breathable air,
  • Keep the entire house cleaner,
  • Help protect mechanical equipment,
  • Help prevent mould and bacterial growth in air conditioner coils and,
  • Help prevent AC condensate drip pans and drain lines from becoming clogged and damaging the furnace.

Electronic Air Purifiers
Air purifiers (not to be confused with HEPA room filters or electronic furnace filters) replace the natural levels of electrical ions and ozone that are missing from indoor air. These portable systems eliminate house odours, including those from pets, smoke, mould and building materials, as well as, help cleanse the air of airborne particles. They require no installation, and just one machine will purify the air in an average size house.

Make-up Air Vents
The installation of a make-up air vent will bring small amounts of fresh oxygenated air into the home while helping to maintain neutral air pressures indoors. They require virtually no maintenance and use no electricity.

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